The present invention relates to a reluctance rotor lamination which is substantially embodied in a circular disk shape. It has a central opening in the center and a flux-conducting section extending radially from the central opening to a connecting ring located on the outer edge of the reluctance rotor lamination along a d-axis (preferred direction of magnetization). The invention also relates to a reluctance rotor having a laminated core made of a plurality of reluctance rotor laminations and a method for the production thereof.
Reluctance rotor laminations of this kind with corresponding openings are known from patent U.S. Pat. No. 5,818,140 A. A laminated core and a corresponding rotor can be assembled from the reluctance rotor laminations. The punched-out sections are used to produce curved, strip-shaped lamination sections that serve as flux-conducting sections and conduct the magnetic flux in the way necessary for the provision of the required reluctance of the rotor. Due to the punched-out sections, air, i.e. a non-magnetic region that acts as a magnetic flux inhibitor, is located between the individual flux-conducting sections. The strip-shaped flux-conducting sections result in a high torque yield. Due to the non-magnetic regions, the magnetic permeability of the laminated core is relatively low in the direction of the q-axis, i.e. the magnetic inhibition direction. The strip-shaped flux-conducting sections extend transversely to the q-axis and, in the circumferential direction, connect adjacent poles of the rotor arranged in each case on the d-axis (preferred directions of magnetization). However, the punched-out sections for the provision of the non-magnetic regions or the formation of the flux-conducting sections result in a weakening of the mechanical stability of the laminated core such that the rotor described is not suitable for high rotational speeds, in particular not for rotational speeds in excess of than 3000 revolutions per minute. For this reason, reluctance motors of the type described are, for example, not suitable for the rotational speeds required for motor vehicles with electric drives.
Therefore, due to the mode of operation, the rotor lamination in a reluctance motor (in short: reluctance rotor lamination) is especially embodied with greatly varying radial stability with respect to the d-axis and q-axis. For example, the d-axis is formed with a flux-conducting section with a continuous lamination from the inner diameter to the outer diameter, while the q-axis is interrupted by flux inhibitors.
For example, the rotor laminations are connected to the shaft by a cylindrical press fit on the shaft. In the case of high speeds, the oversize of the press fitting should be higher, since the centrifugal force results in an expansion of the inner diameter of the rotor lamination and the torque transmission onto the shaft is reduced. In addition, feather keys for torque transmission would be unfavorable since the groove to be introduced into the laminations would further reduce the stability.
The different degrees if stability in the axes results in different degrees of deformation during the pressing-on and hence in impermissible stresses on the outer ribs or on the outer connecting ring of the rotor lamination, in particular on the rib directly next to the d-axis. The continuous material in the d-axis passes as a deformation from the inner diameter to the outer diameter, while in the adjacent region, due to the flux inhibitors, there is no deformation from inside to out.
In addition, the ribs holding the flux-conducting sections together are subject to extreme stress from the centrifugal force on rotation. In the case of a relatively high tensile stress, which can actually be caused by the press fit, there is no reserve or only little reserve for the centrifugal force loading. Therefore, a reluctance rotor of this kind is only suitable for relatively low speeds.
One possibility for optimization consists in the integration of closing shapes between the shaft and the rotor lamination to enable the withdrawal of the press fit forces with the simultaneous transmission of a high torque. The closing shapes used could be grooves and springs, flat parts or even shafts with polygonal cross sections. Although these measures do enable tensile stresses to be avoided as there is no need for press fitting, as indicated above, in some circumstances the lamination is also destabilized by grooves and the production or connection of the shafts is complicated.